Elevator control system



Jane 19, 1934. B DE 1,963,484

ELEVATOR CONTROL SYSTEM Filed March 2, 1933 4 Sheets-Sheet l IN VEN TORBy W74 iZATTORNEY.

June 19, 1934. H, BORDEN 1,963,484 ELEVATOR CONTROL SYSTEM Filed March2, 1935 4 Sheets-Sheet 2 v L? asv T T ,Sc

du5\ J .aH

IN VEN TOR.

* T ATTORNEY.

I June 19, 1934. H, BQRDEN I 1,963,484

ELEVATOR CONTROL SYSTEM Filed March 2, 1933 4 Sheets-Sheet 3 I I J I J52I V 13 Z2 INVENTOR- 7 wxew ATTORNEY.

June 19, 1934. J BORDEN 1,963,484

ELEVATOR CONTROL SYSTEM Filed March 2, 1933 4 Sheets-$heet 4 I 23 I? .29+Laz [I :3 52 I 18 0 I 1 I I i A} q Q q n1 I l] 45 I I I I I 55a l 22 211 LIE ATTORNEY.

Patented June 19, 1934 I ELEVATOR CONTROL SYSTEM Joseph H. Borden,Elkins Park, Pa.

Application March 2, 1933, Serial No. 659,324

A 20 Claims.

My invention relates to methods of and apparatus for controllingelevators and the like, and.

particularly, for high speed elevator systems.

In accordance with one aspect of my invention, as an elevator car, orequivalent, approaches a 'pre-selected landing or floor, the energy tothe car motor is progressively reduced at points whose distances fromthe desired landing vary in accordance with speed of approach of the carto the landing to ensure rapid and smooth deceleration of the car and tobring the car to a stop level with the floor, without need forre-leveling.

Further in accordance with my invention, the aforesaid reductions arecontrolled by spaced elements, whose positions correspond to theposition of the car, and which successively cooperate with a controlledmember whose position is determined by the speed of the car, or morespecifically, the speed of the car and the concurrent load of the carmotor.

In accordance with another aspect of'my invention, vanes, or equivalent,preferably carried by a rotatable drum in spaced relation are moved bythe car to intercept light to a photo-cell, or

. the like, the resulting and successive change of current in thephoto-cell circuit effecting successivereductions of the energy suppliedto the car motor; more specifically, the photo-cell is carried by theabove controlled member in order 3 that the speed, or load and speed, ofthe car shall vary the relative positions of the vanes and thephoto-cell for any given position of the car.

My invention further resides in the system and arrangement hereinafterdescribed and claimed.

Fig. 1 diagrammatically illustrates an elevator system embodying theinvention.

Fig. 1a is a modified form of motor connection.

Fig. 2 is a simplified wiring diagram of the system of Fig. 1.

Fig. 3 is a detail view on enlarged scale of a control device includedin the system of Fig. 1.

Fig. 4 is an end view of Fig. 3.

Fig. 5 is a detail view on enlarged scale of the optical system of thecontrol device of Fig. 3.

Fig. 6 illustrates a control arrangement appli cable to the system ofFig. 1.

Referring to Fig. 1 which is exemplary of a typical elevator systemembodying the invention, the motor 1 for raising and lowering the car 250 is energized from the generator 3 which is driven by motor 4connected across the line L1, L2 supplied by a suitable source ofcurrentPP (Fig. 2). The direction and speed of motor 1 is controlled bythe car switch 5, or equivalent, which through relays A to G, as morespecifically hereinafter described, controls the direction and amplitudeof current through the shunt field 6 of the generator for variation ofvoltage applied to the motor 1.

Assuming that the car is stationary and it is so desired to go to ahigher floor, the car switch 5 is swung in clockwise direction ,first toengage contact U1 which energizes the up" contactor A, the closure ofwhose contacts A1, A2 completes a circuit through the field 6 ofgenerator 3, and provides for flow of current through the field inproper direction for hoisting by motor 1. The circuit completed by thecontacts A1, A2 includes all of r sistance R in series with the shuntfield 6 so tha the voltage generated is low for correspondingly lowspeed of motor 1. The closing of contact U1 of the car switch alsoeffects release of the usual solenoid brake (not shown). The car switchnext engages contact U2 to complete a circuit through the coil of relayD 7 5 whose co'ntact,Dl, thereupon moves to shunt the section d ofresistance R so that the output voltage of generator 3 is increased toincrease the speed of motor 1. Similarly, continued movement of the carswitch'efiects engagement of contact U3 which effects energization ofrelay E whose contact E1 is thereupon actuated to shunt the section e ofthe generator field resistance R further to increase the speed ofhoisting of the car. I

When the car switch engages contact U4, the relay F is energized toshunt the section 1 of the generator field resistance R by its contactF1 so that the motor runs at fourth speed. The contact F2 of relay Fcloses the circuit of relay H through contact C1 of relay C which wasenergized concurrently with energization of relay A, whereupon contactH1 closes to complete a lock-in circuit for fourth-speed relay H whichincludes ,contact '01 of relay C. Contact 1-12 of relay H irfseries withcontact C2 of relay C and contact A3 of relay A completes a lock-incircuit for relays A and C. Contact H3 of relay H in series with contactD2 of relay D completes a lock-in circuit for second-speed relay D.Contact H4 of relay H in series with contact E2 of relay E completes alock-in circuit for thirdspeed relay E. Similarly contact H5 of relay Hin series with contact F3 of relay F completes a seal-in circuit for thefourth-speed relay F.

Movement of the car switch to its final or fifth-speed position closescontactlU5 to effect energization of relay G whose contact G1 shuntssection g of the generator field resistance R. C ntact C2 of the relay Gcompletes its seal-in circuit. The car is now being hoisted at maximumspeed for example, at the rate of about 600 feet per minute.

In accordance with the present invention, the operator wishing to makean automatic stop at one of the upper floors, returns the car switch tocenter position suitably in advance of that floor. This operation leavesall of the foregoing relays locked in circuit and closes the contact CS.

For clarity of further explanation, it is assumed that the approximatedistances at which the different speeds are cut-out are as follows: highspeed, 12 feet; fourth speed, 6 feet; third speed, 3 feet; second speed,1 feet; and first speed, four inches. As will hereinafter more clearlyappear the actual point of cut-off of first and second speeds are madeto vary in accordance with the load and speed of the car.

As the car reaches a position 12 feet below the desired floor, the carswitch having been previously closed contacts SSU are closed bymeehanism correlated to position of the car hereinafter morespecifically described, to complete, through the closed contacts CS ofthe car switch and closed contact A4 of relay A, a circuit in shunt torelay coil G effectively to de-energize it.

Contact G1 thereupon opens to insert resistance section (7 in thegenerator field circuit to effect deceleration of the car; contact G2opens to break the seal-in circuit of relay G; and baclccontact GS ofthe relay closes.

When the car arrives at a position 6 feet below the desired floor,contact 4SU is closed, by the aforesaid mechanism to be hereinafterdescribed, to complete, through ear switch CS, contact A4 of relay A,and back-contact GB of relay G, a circuit in shunt to relay coil E whichis thereby effectively de-energized. The contacts F1 of the relay opento introduce resistance section f into the generator field circuit forfurther deceleration of motorl. Contacts F3 open to brealr the hold-incircuit of the relay F. The back contacts F; of the relay close tocomplete through closed contacts C1 of relay C and closed contact 1-11of relay H circuit including the lamp or bulb 8, whose purpose willhereinafter be explained.

The closing of contact F4 also completes a circuit through the coil ofnotching relay I which moves contact arm 9 to its first position. In ashort time, the filament of lamp 8 heats to sufficient brilliancy tocause the photo-electric cell 12 to effect energization of relay K whosecontact K1 opens to de-energize coil I of the notching relay, arm 9remaining held in its deflected position by pawl 11.

When the car arrives at a position approximately three feet below thedesired landing, the vane 13U, as hereinafter described, momentarilyintercepts the beam of light from bulb 8 to photocell to effectde-energization of relay K, whose I contact K1 in closing againenergizes the notching relay I to advance arm 9 to engagement withcontact 9E. In this second position, the arm 9 shunts the relay E whosecontact E1 thereupon opens to effect further reduction of the motorspeed by reinserting section e of generator-field resistance R. ContactE2 of the relay opens to break its seal-in circuit.

When the car running at reduced speed arrives at approximately eighteeninches from the floor, vane MU momentarily interrupts the light beam toeffect movemert of arm 9 to its'tbird position in engagement withcontact 9D to shunt relay coil D. The contact D1 of the relay opens toreinsert section (1 of the generator-field resistance in circuit.Contact E2 opens to break the hold-in circuit of the relay.

When the car running at low speed reaches a point about four inchesbelow the landing, vane 15U momentarily intercepts the light beam to thephoto-cell whereupon arm 9 moves to its final position in engagementwith contact to shunt out the relay coil C. Contact C2 of the relayopens to break the circuit of relay A whose contacts Al, A2 thereuponopen to breal: the circuit of the generator field 5 so that current isno longer supplied to the car motor 1 and simultaneously withde-energization of the motor, the brake is applied to bring the car to astop. The back.- contacts A5, B5 may be utilized to complete a ch. cuitacross the generator output circuit including the differential fieldwhich prevent generator 3 from functioning as a series generator.Contact C1 of the relay opens to brealr the circuit lay H and of lamp 8.Contact C3 the closes to energize coil J to lift pawl ll. wher spring 16or equivalent returns a. n 9 to its original or first position at whichopens switch 10 to tie-energize coil J. All of the elements are now inthe same position as at the beginning of the run.

The slowing down of the motor in several steps avoids jarring or jcltingof the car, and particularly with the compensating system hereinafterdescribed ensures that the car will stop level with the landing withoutneed for releveling either automatically, or manually.

If less than a twofloor run is to be made, the operator should move thecar switch to the fourth speed contact H4 in which event relay G is notenergized and the automatic stopping will be initiated by contact 4SU.The operation is otherwise as above described.

The operation for down direction of the car is similar; the car switchis swung counter-clockwise successively to engage the down contact DNlto BN4, or DNl to BN5, which effects acceleration of the car motorsubstantially as above described; the only difference is that the downrelay B is energized instead of the up relay 4 to effect flow of currentthrough the generator field 6 in proper direction.

For illustration of the mechanism for operating contacts 5SU, 4SU, 58D,48D, reference is made to Figs. 3 and 4. The control cable 17 which iswound around the control drum i8 and passes over the lower pulley 19 isconnected to the car so that the drum 18 is rotated as the car changesits position. Preferably the cable 1'7 is divided into two sections, oneof which starts from the top of the car, winds around the drum and isanchored to one end of drum, and the other of which starts from thebottom of car, passes around sheave 19, leads up to drum and is anchoredon the opposite end of drum from the first section. In addition to itsrotation, the drum changes its position along its axis of rotation withchange in position of the car due to threaded engagement with thethreaded shaft 20 whose opposite ends are secured to the standards 21,21 extending upwardly from the base member 22.

The groove 23 of the drum receives the end of the member 24 whichextends upwardly from the carriage 25 which is movable along the rails26. Each of the switch operating members 2'7U supported by the carriageare adapted to operate the switches 5SU, 4SU in succession as the car inits upward movement passes the 12 foot and 6 foot points below eachfloor; similarly. the members 27D are adapted to operate the switches58D, 45D K50 in succession as the car in its downward movement passesthe slowdown points above each fioor. The operation of these switches isof course without effect upon the speed of the car unless car switch 5has been centered to close contacts CS which are in series with 5SU, 4SUetc., as most clearly shown in Fig. 2.

While additional switches of this type could be used automatically tocut-in sections of resistance R at definite fixed distances from thedesired floor, I prefer to have the distances at which final sectionsare out in, variable in accordance with actual running conditions as thecar approaches the desired landing. The speed at which the car mayapproach any landing is determined by many variable factors astemperature eflect upon the equipment, condition of the commutator andbrushes of the motor and generator, the load of the car, length of run,condition of the rails, etc.

The arrangement now described ensures that the car Will be broughtsmoothly to a stop, level with the desired landing, and regardless ofall of these variable factors, without need for releveling andnotwithstanding the high speed at which the to the position shown inFig. 4 by springs 32 or equivalent.

The vanes 13U, 13D, etc., above mentioned, a set of each for each fioorare arranged helically along the periphery of the control drum. 18 sothat each in turn passes through the slot 33 of housing 29 to interceptthe beam of light from lamp 8 to the photo-cell. Preferably as shown inFig. 5, the mirror 34 reflects light from the lamp 8 to mirror 35 whichin turn reflects it to a light-responsive device, as the photo-cell 12,and the vanes pass through the focal point of the lens 36 between themirrors. The photo-cell is preferably of the type generating currentupon exposure to light, though a photo-cell of any of theresistance-variation types may be utilized. In the car case the jumper xis removed and a suitable source of current inserted in circuit.

It is understood that for each intermediate floor there is a set of upvanes and a set of down vanes which control the notching relay I throughthe photo-cell and relay K of course, only one set of vanes is neededfor the top and bottom fioors, as they are approached by the car fromonly one direction. As thus far described, the vanes efiecting cut-outof sections of resistance R at definite or fixed differences from thechosen landing in generally the same manner'as contacts 5SU, 4SU or 58D,48D.

While the system thus far described has many advantages, I prefer to addcompensation for variations in the load and speed of the car. Exactleveling by varying the cut-off points in accordance with existingconditions is accomplished by the torque motor T which positions theframe 31, 30 carrying the master-control housing 29 in the properdirection and to proper extent from the neutral position shown.

The circuit of the torque motor may be completed by the back contact E3of relay E which is de-energized during automatic slow-down to secondspeed as above described, or more preferably,'closing of back contactE3shunts resistance TR fully to energize the motor. The torque motor isconnected across the motor supply circuit in series with the armature 37of the auxil- Eg=KI where Eg auxiliary generator voltage I=current to orfrom armature of motor 1.

For any given generator voltage, part is consumed in overcoming thearmature resistance and the remainder in overcoming thecounter-electromotive force of the armature; the lower the armaturespeed, the less the counter-emf and the greater the motor current andvice versa, i. e.,

EazRl+Eor where Ea voltage impressed on the armature of motor 1Eor:counter-electromotive force of armature R armature resistanceI=armature current The voltage applied to the torque motor is thealgebraic sum of the voltage impressed on motor 1 and the voltagegenerated by the auxiliary generator: i. e.,

The effective output voltage of the auxiliary generator by design or bya suitable voltage dividing network, as potentiometer P, can be chosento equal RI, or armature drop so that the torque motor voltage isproportional to the speed of the armature, i. e., the torquemotorvoltage is proportional to the speed at which the car isapproaching the landing.

Preferably by design, or adjustment of potentiometer P, the voltageintroduced by the auxiliary generator in series with the torque motor ismade to be greater than RI so that the voltage Eg is not only sufficientto cancel the RI component of the motor voltage but includes a furthercomponent varying with the load of the car. In other words, the voltageapplied to the torque motor, at least during the stopping region; is acompositefunction of the speed and load of the car and since the voltageimpressed on the torque motor determines the position of the controlhousing 29, the distances from the desired landing at which the relaysare out out by the control vanes are each .determined by load and speedof the car.

Consequently, for example, if the car is approaching the desired upperlanding at high speed and light load, the arm 31 is further to the left(Fig. 1) to meet plate 15U than for lower speed and/or lighter load.Moreover arm 31 follows the slow-down of the car so that the distancesat which the plates 14U, and 13U intercept the light beam for furtherslow-down are each actually determined by the speed of the car asaffected by the previous control. The system op- .erates properly underconditions of hoisting, lowering, regenerating or motoring, the polarityof the auxiliary generator reversing automatically since its fieldcurrent changes direction with change of direction of current throughthe motor armature.

In many cases for very accurate compensation at all speeds, it isdesirable to obtain a slightly rising torque-voltage characteristic ofthe torque motor. This is attainable by use of a compound wound torquemotor in lieu of a simple shunt motor. In Fig. 1a are indicated theslight tit changes necessary. Briefly, the armature circuit of thetorque motor is opened by removal of jumper y, and the conductors 3 1/of Fig. 1a are connected to the terminals formerly bridged by the jumperto include the series field I'FS of the torque motor in circuit wheneither relay A or relay B is energized. 'I'he contacts A7, A8 of relay Aand contacts B7, 138 of relay B constitute a reversing switch so thatthe excitation of the series field is always in the same sense as theexcitation of the shunt field 'IF. The resistance FSR in shunt to theseries field TFS is preferably variable to allow adjustment of thetorque-voltage characteristic to meet the requirements of theinstallation.

The advantage of having the torque motor circuit closed in advance ofclosing of the back contacts of relay 3 lies in the fact that tendencyof the arm 31 to overshoot or hunt its proper position is avoided. Thevalue of resistance TR is chosen high enough to limit the current to thetorque motor during high speed running of mo tor 1, to safe values, andlow enough so that arm 31 is held against one or the other of stops 38depending on whether the car is running up or down.

The control drum and its accessories may be located in the pent house,or other suitable location, where they are readily accessible foradjustment, replacement or repair.

By addition or the arrangement shown in Fig. 6, the car may becontrolled by push-buttons, or the like, at or corresponding to thelandings. Briefly, the contacts U1 to U4, for signal control,

- are connected respectively to the contacts ill to w: of the up relay Mand correspondingly the contacts Bill to BN4 of the car switch areconnected respectively to the contacts dnl to dn4 of the down relay N.I'he wire 35 is disconnected from the off-point of the car switch andthe circuit from L1 to the off-point is completed through the backcontacts CS1 and CS2 of relays S and 'I'. Contact U5 of the high-speedup relay S and 6125 of the high speed down relay T are connected to thepoint U5 and BN5 respectively of the car switch. In effect, the relays Mand N replace or supplement the car switch.

For simplicity of explanation, it is assumed that there are four'iioors. With the car at the first floor. the member UD, carrying thecontacts MC. ND, SC and TC connected respectively to the re lays M, N, Sand T, is in the position shown; with the car at the second floor,contact ND is in engagement with the down contact lSD; contact MC inengagement with the up contacts 3SU and 4SU; and contact SC is inengagement with contact ll-IU. With the car at the third floor, contactND is in engagement with contacts lSD and 2813; contact MC is inengagement with contact QSU; and contact TC is in engagement withcontact lHD. With the car at the fourth floor, contact ND is inengagement with contacts 18D, 28D, and BSD; and contact TC is inengagement with contacts LED and 2HD.

Assuming the car to be at the first floor, and that button 4? at thefourth floor, or button 40, the fourth-floor button in a control panelin the car has been pushed; the relay 4L is energized to close contacts4S which completes a hold-in circuit for the relay and effectsenergization of relay M through a circuit which includes contacts MC andSU; contact ll-I of the relay 4L completes a circuit through relay S ascontacts SC and ZHU are closed. With the relays M and S energized, theresult is the same as if the car switch had been moved to engagecontacts U1 to U5, i. e., the car moves upward at high speed. Before thecar reaches the position for which the fourth floor 5SU contact isengaged (Figs. 1, 2), the contacts SC pass beyond contact 4HU tode-energize relay S. The closure of the back contact CS1 of relay Seffects the same result as centering of the car switch, and the car isbrought automatically to a. stop as above described.

If the third floor button 3F, or 3C, is pushed with the car at the firstfloor the operation is similar. However, if the second floor button 2F,or 20, is pushed with the car at the first floor, the high-speed up"relay is not energized, and the car runs at slow speed as if in thesystem of Fig. l the operatorjdoes not move the car switch beyond the 4Ucontact. The car is brought automatically to a stop level with theselected floor.

In general with the push-button control system of Fig. 6, the car willrun at high speed and automatically stop for a long run, as of two ormore floors, and will run at lower speed and automatically stop for aone floor run.

While I have illustrated and described a preferred embodiment, it is tobe understood that my invention is not limited thereto but isco-extensive in scope with the appended claims.

What I claim is:

1. In the art of controlling elevator cars or the like, the method ofaccurately stopping the car at a desired landing which comprisesproducing an effect of magnitude dependent upon the speed of approach ofthe car toward said landing, and discontinuing application of drivingpower to the car upon its arrival at a point whose distance from thedesired landing is dependent upon the magnitude of said effect.

2. In the art of controlling elevator ears or the like, the method ofaccurately stopping the car at a desired landing which comprisesproducing an effect whose magnitude is a function of the speed of thecar and of the power concurrently delivered to its driving motor, anddiscontinuing application of driving power to the car upon its arrivalat a point whose distance from the desired landing is dependent upon themagnitude of said effect.

3. In the art of controlling elevator cars or the like, the method ofaccurately stopping the car at a desired landing which comprisesproducing an effect whose magnitude is determined by the speed of thecar, and effecting successive reductions of the driving power applied tothe car at points whose distances from the desired landing are dependentupon the magnitude of said effect.

4. In the art of controlling elevator cars or the like, the method ofaccurately stopping the car at a desired landing which comprisesproducing an effect whose magnitude is a function of the speed of thecar and the concurrent load upon its driving motor effecting successivereductions of the driving power applied to the car at points whosedistances from the desired landing are dependent upon the magnitude ofsaid effect.

5. An elevator system comprising a car, a motor for hoisting andlowering, and means for effecting deceleration of said motor comprisinga circuit and photo-cell therein, a source of light, structure forrepeatedly interrupting light from said source to said cell as said carapproaches a landing, relays, and means responsive to impulses ofcurrent in the photo-cell circuit for effecting successive actuation ofsaid relays to reduce the power supplied to said motor.

6. An elevator system comprising a car, a

motor for hoisting and lowering, and means for effecting deceleration ofsaid motor comprising a single circuit-controlling device, means forrepeatedly actuating said device assaid car approaches a landing,relays, and a notching relay erator for supplying current to said motor,and

control means for said voltage-varying means comprising acircuit-controlling device, means for repeatedly actuating said deviceas the car approaches a landing, and means including a notching relayresponsive to successive actuations of said device for progressivelydecreasing the voltage of. said generator.

'8. An elevator system comprising a car, a motor for hoisting andlowering, a variable voltage generator for supplying said motor, andcontrol means comprising a circuit and photo-cell therein, a source oflight, structure for repeatedly interrupting light by said source tosaid cell as said car approaches a landing, and means responsive toimpulses of current in the photo-cell circuit for progressively.decreasing the generator voltage.

9. An elevator system comprising a car, a motor for hoisting andlowering, a generator for supplying said motor, a resistance, relays forinserting sections of said resistance in the field circuit of saidgenerator, and control means comprising a circuit and photo-celltherein, a source of light, structure for repeatedly interrupting lightfrom said source to said cell as said car approaches a landing, andmeans responsive to successive impulses of current in the photo-cellcircuit for effecting actuation of said relays in succession todecelerate the car.

10. An elevator system comprising a car, a motor for hoisting andlowering, relays actuatable to reduce the power to said motor, a control-member movable concurrently with said car, a

circuit and photo-cell therein, a source of light, structure carried bysaid member repeatedly to preclude transmission of light from saidsource to said photo-cell as the car approaches a landing, and meansresponsive to successive current impulse in the photo-cell circuit foreffecting actuation of said relays in succession.

11. An elevator system comprising a car, a

motor for hoisting and lowering, and means for or retard the position ofsaid photo-cell in accord-,

anee with car speed, and means responsive to interruption of the lightfor effecting reduction of power to the motor.

12. An elevator system comprising a car, a motor for hoisting andlowering, and means for de-energizing the motor as the car approaches adesired landing at a distance from the landing determined .by the speedof approach of the car, comprising structure movable concurrently withsaid car and co-acting structure so mounted that it may be advanced orretarded, and means for varying the position of said coacting structurein accordance with the speed of the car and the load upon said motor.

13. An elevator system comprising a car, a motor for hoisting andlowering, and means for de-energizing the motor as the car approaches adesired landing at a distance from thelanding determined by the speed ofapproach of the car, comprising a photo-cell, a source of light,structure movable concurrently with said car for controllingtransmission of light from saidsource to said cell, means for mountingsaid cell so that its cooperation with said structure may be advanced orretarded, and means responsive to the speed of approach of the car andthe motor load for controlling said mounting means to determinethe-position of said photo-cell relative to said structure.

14. An elevator system comprising a car, a motor for hoisting andlowering, a variable volt age generator for supplying the motor, acircuit and photo-cell therein, a source of light, structure movableconcurrently with said car repeatedly to interrupt transmission of lightfrom said source to said cell as the car approaches a landing,.anauxiliary generator, a torque motor for nected in series with saidauxiliary generator in a. path in shunt to the car motor, and meansresponsive to current impulses in the photo-cell circuit for decreasingthe voltage of said generator.

15, An elevator system comprising a car, a

-motor for hoisting and lowering, said car, and

means for effecting deceleration of said motor to stop the caraccurately at a desired landing comprising spaced elements movable inaccordance with movement of the car, relays for reducing the powersupplied to said motor, and a circuit-controlling device coacting withsaid elements in succession repeatedly to close a single circuit toeffect actuation of said relays in succession. I

16. An elevator system comprising a car, a motor for hoisting andlowering, and means for effecting deceleration of said motor comprisinga single circuit-controlling device, means for repeatedly actuating saiddevice as said car ap proaches a landing, relays for reducing the powersupplied to said motor, and means responsive to successive actuations ofsaid device to effect actuation of said power-reducing relays insuccession.

17. An elevator system comprising a car, a motorfor hoisting andlowering, a variable voltage generator for supplying current to saidmotor, and control means for said voltage-varying means comprising acircuit-controlling device, means for repeatedly actuating said deviceas the car approaches a landing repeatedly to change the impedance of acircuit, and means included in said circuit to effect progressivedecrease of the.voltage of said generator.

18, An elevator system comprising a car, a driving motor therefor, meansfor producing an effect varying in magnitude in accordance with thespeed of the car, and means for de-energizing the motor as thecarapproaches a desired landing, responsive to said effect to determine thedistance from the landing at which the car is de-energized differentlyfor each different speed of approach of the car to the landing.

19. An elevator system comprising a car, a driving motor therefor, meansfor de-energizing the motor as the car approaches a desiredlandcontrolling the position of said photo-cell coning, comprisingstructure whose position is a. continuous function or the position ofthe car, and co-acting structure whose position is a. continuousfunction 01' the speed of approach of the car to the landing.

20. An elevator system comprising a. car, a driving motor therefor,means for producing an eiiect whose magnitude is jointly determined by

